I've seen them, but didn't think to take a photo. We were waiting in a line at the end of the MK (I stopped for EVERY PHOTO) and they shouted at us that we needed to catch up to them after the photo, and might want to get out of the line. They didn't pass you without letting you know. Like an idiot I waited for the photo, then ran-ran-ran until they were out of my sight. I think that unless you get swept really early on (and are therefore WAY behind pace) they give you a lot of warning.